By Kate Abnett BRUSSELS (Reuters) – As Patricia Espinosa prepares to step down as U.N. climate chief, she has a warning for the world: Russia’s invasion of Ukraine must not distract leaders from the escalating climate crisis. Even as the war is causing “so much suffering”, global warming remains the “most rapidly growing threat to human species on the planet”, Espinosa told Reuters. Espinosa said she planned to step down as executive secretary of the U.N. Framework Convention on Climate Change (UNFCCC) when her second, three-year term ends in July. The UNFCCC is the 196-country treaty that con…